<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div{
            background: ;
        }

    </style>
</head>
<body>
    <div style="height: 1000px">
        <div style="height: 300px; width: 100px; border: 1px solid red; position: relative">
            <div style="position: absolute; bottom: 0; right: 0;">返回</div>
        </div>
        <div style="position: fixed; bottom: 0; right: 0">返回</div>
    </div>
</body>
</html>